How to make a homemade black powder M-80 To make the M-80 you will need a rocket tube with an inside diameter of 3/8 of an inch. Put a sheet of paper on a table and stand the rocket tube up on it's end. Take some bentonite clay and put it about 1 1/2 teaspoons it down into the tube. Take a rod and use it as a rammer. Put it down into the tube and compact the clay to close up one end of the tube. Use your spoon to tap on the rammer. After you pack it into the tube, turn it upside down and empty the excess clay onto the sheet of paper so that you can put it back in the clay container. Take a hole punch and punch a hole in the center of the tube making sure that you only poke a hole in one wall of the tube. Fill the tube with black powder and then put the bentonite clay to fill in the end of the tube. Do not use the rammer on the black powder. Once you have put the clay into the end of the tube use the rammer to pack the clay into the end of the tube. But do not tap it with the spoon just use your hand to pack it in. Put the fuse into the hole and put a pencil with the sharpened end into the hole beside the fuse and break it off to hold the fuse tight. Now you can take your creation and blow it up.